Agriculture Reference
In-Depth Information
2
Anatomy
There are four main types of tissues in animal bodies:
Descriptive terms
Certain terms are used to describe the exact position and
direction of the different body parts, assuming that the
animal is in the standing position:
Dorsal, superior or upper structures or positions lie
towards the back or dorsum of the body, head or tail.
Ventral, inferior or lower positions are directed
towards the belly or venter.
The longitudinal median plane divides the body into
two similar halves. Structures that are nearer than others
to the median plane are said to be medial or internal,
while those farther away from it are lateral or external.
Planes parallel to the median plane are sagittal to it. Parts
which lie towards the head are cranial or anterior, while
those towards the tail are caudal or posterior.
In relation to the limbs, the terms proximal and distal
are used, those lying towards the junction with the body
being proximal and those at a greater distance away from
the body being distal. Above the knee and hock, the
terms cranial and caudal are used for front and rear posi-
tions, those below the knee and hock being dorsal and
palmar and dorsal and plantar, respectively.
The terms superficial and deep denote relationships
from the surface of the body, for example, superficial and
deep flexor tendons of the legs.
1
Epithelial tissues are found on external and internal
surfaces and also form specialised structures such as
the liver.
2
Muscular tissues, constituting the flesh of animals, are
of three main types: voluntary (striped, striated),
involuntary (unstriped, unstriated, smooth) and car-
diac (a special form of striated muscle found in the
heart).
3
Connective tissues include the skeleton, which gives
rigidity to the body. Blood is a specialised form of
connective tissue although it is sometimes classified
alone.
4
Nervous tissue is the most specialised of all the tissues.
It transmits the nerve impulses of both sensation and
movement.
The animal body is a highly developed multicellular
organism, consisting of billions of cells specialised to
form tissues. Each tissue has a special function; the tis-
sues are further grouped together to form organs. An
organ is a group of tissues arranged in a special manner
to carry out a special task, for example, the heart, stom-
ach, kidney and bone. Organs are again grouped to
form systems, each of which performs essential body
functions.
The systems of the body are 11 in number, as follows:
osteology and arthrology (bones and joints), digestive,
respiratory, circulatory, lymphatic, urogenital, nervous,
endocrine, myology (muscles), sense organs (ear, eye,
organ of smell and organ of taste) and common integu-
ment (skin and appendages).
Osteology and arthrology
Bones
The skeleton, composed of some 200 bones, acts as a
support and protection for the soft tissues of the body
and provides a system of levers for locomotion and body
